NEC completed the 523 magnetic drum unit as an external memory for the NEAC-2230 and NEAC-2206, and exhibited it as part of the NEAC-2230 and NEAC-2206 at the first Japanese-made electronic computer show in November 1962.
This unit housed an IR-812 magnetic drum unit together with electronic circuits for writing, reading, band selection and other tasks.
NEC also completed the IR-811 magnetic drum unit which used the same magnetic drum, but expanded memory capacity by increasing the number of tracks and improving the recording system.
(The photo does not show the 523 magnetic drum unit. It shows the IR-811 magnetic drum unit which used the same magnetic drum.)
| Model name | IR-811 | IR-812 (Use in 523 Magnetic Drum Unit) |
|---|---|---|
| Drum dimensions(mm) | 320ø×365 | 320ø×365 |
| Rotation speed(rpm, at AC60Hz) | 3500 | 3500 |
| Number of information tracks | 250 | 200 |
| Memory capacity in 1 cycle(bit) | 7,000 | 3,250 |
| Total memory capacity(bit) | 1,750,000 | 650,000 |
| Applications | - | NEAC-2230,NEAC-2206 |
